Mixed martial artists don't need much motivation to knock each other senseless. They train for countless hours for matches that last only a few minutes, and nobody wants the loser's paycheck—or bruises.

Then you have Miesha Tate and Ronda Rousey. The rivalry between these fighters is similar to Bears-Packers—it's obvious to everyone and can be downright nasty.

Rousey and Tate bring their mutual hatred to the latest season of "The Ultimate Fighter," the first coed season of the Fox Sports 1 reality show. But instead of combatants in the octagon, they're opposing coaches.

That is, until they rematch Dec. 28 (Rousey won the first bout in March 2012 by forcing Tate to submit).

RedEye spoke with Rousey and Tate—separately, for our own safety—last month in Chicago to get the lowdown on why these two make each other miserable.

Tate's version: "She was coming into Strikeforce; she talked about dropping down to 135 [pounds] and slapping that title out of my hands. I was like 'Oh, you're just going to slap it out of my hands?' I was like, 'Gosh that was disrespectful.' I would never talk to a champion that way. I took immediate disrespect."

Rousey's version: "It started when she answered a fan question and expressed interest in fighting me on Twitter. I said that I was down, and after my next fight, I asked for the title match and she said that I didn't deserve to fight her."

Stage 2: Tate's boyfriend joins the fray on Twitter. (March 2012)

"He said he was going to knock my teeth down my throat," Rousey said. "He did this the night before me and Miesha fought. Instead of telling her that she has a world title fight tomorrow and that she should go to bed and rest, she was up for hours defending him on Twitter instead of preparing for her fight."

"We spent six weeks filming 'The Ultimate Fighter' that you guys haven't seen," Rousey said. "So there was a lot that went on that you guys don't know and that we can't talk about.

"I have an all Armenian team pretty much; I take very seriously offenses that are of those close to me, more than any offenses to myself. I don't think she's ever going to have an Armenian fan again."

Stage 4: Tate vows revenge in their rematch. (August 2013)

"[Rousey] got under my skin and really got the better of me. My new perspective is to take it with a grain of salt. That's the biggest thing about women's MMA that's different than the men's; the mental and emotional warfare is so powerful, so strong. I think guys can say something, piss each other off, then they fight and they're totally over it. Women hold onto it till the bitter end."